General electronic sphygmomanometer manufacturers will provide free electronic sphygmomanometer calibration, you can go to the manufacturer to calibrate, you can also calibrate their own. Own calibration of electronic sphygmomanometer to consider three factors, cuff airbag size, pressure sensor accuracy, algorithm accuracy, cuff airbag size can be measured with a ruler, and then compared with the upper arm circumference, the accuracy of the pressure sensor will be tested before the factory, algorithm accuracy can be compared with smart phones. Electronic sphygmomanometer calibration should be compared with the mercury sphygmomanometer, first use the mercury column sphygmomanometer to measure blood pressure, rest for 3 minutes and then use the electronic sphygmomanometer to measure, then rest for 3 minutes and use the mercury column sphygmomanometer to measure, compare the results of several measurements, the difference between the electronic sphygmomanometer and the mercury column sphygmomanometer should be less than 5mmHg, if more than 5mmHg, it means that the electronic sphygmomanometer is not accurate.